diff --git a/knowledge base/cloud computing/aws/rds.md b/knowledge base/cloud computing/aws/rds.md
index 00f692a..12bdfc2 100644
--- a/knowledge base/cloud computing/aws/rds.md
+++ b/knowledge base/cloud computing/aws/rds.md
@@ -331,6 +331,12 @@ created manual snapshots to recover it.
Taking backups can be unbearably slow depending on the amount of data needing to be copied.
For reference, the first snapshot of a DB instance with standard 100 GiB `gp3` storage took about 3h to complete.
+AWS charges only for snapshots that one owns. Public snapshots _owned by other accounts_ are **not** counted.
+AWS does **not** charge for backup storage of **automated** snapshots up to the size of an RDS instance, as long as
+that instance is active. Any backup storage beyond this incurs additional charges.
+Manual snapshots are billed **entirely** based on their storage usage.
+Cross-region snapshot copies also incur additional transfer and storage charges in the destination region.
+
### Automatic backups
Automatic backups are storage volume snapshots of **entire** DB instances.
@@ -369,13 +375,14 @@ Automated backups will **not** occur while a DB snapshot copy is running in the
### Manual backups
Back up DB instances manually by creating DB snapshots.
-The first snapshot contains the data for the full database. Subsequent snapshots of the same database are incremental.
+The first snapshot contains the data for the **full** database. Subsequent snapshots of the same database are
+**incremental**.
One can copy both automatic and manual DB snapshots, but only share manual DB snapshots.
-Manual snapshots **never** expire and are retained indefinitely.
+Manual snapshots **never** expire and are retained until explicitly deleted.
-One can store up to 100 manual snapshots per Region.
+One can store up to **100** manual snapshots per Region.
### Export snapshots to S3
@@ -1022,7 +1029,7 @@ Impacting factors (from most to least impactful):
1. Storage type and capacity.
1. Backup storage.
- Backup storage up to 100% of one's total database storage (per region) is free.
+ Backup storage _for automatic snapshots_ up to 100% of one's total database storage (per region) is free.
Additional backup storage costs ~$0.095 per GB-month (`us-east-1`).
[Exporting snapshots to S3][export snapshots to s3] costs ~$0.10 per GB (`us-east-1`).
@@ -1043,6 +1050,10 @@ Impacting factors (from most to least impactful):
1. Zero-ETL integrations.
1. Extended support.
+1. Networking.
+
+ Public IPv4 addresses associated with resources launched in a VPC are charged at standard rates.
+ This rate is $0.005/h as of 20126-02-13, and is charged in 1s increments for a minimum of 60s.
### Cost-saving measures
@@ -1050,9 +1061,9 @@ Impacting factors (from most to least impactful):
Consider changing them more appropriate ones (more recent, smaller, or Graviton-based) every few months.
- Consider leveraging [reserved instances][rds reserved instances].
- Prefer using _Standard RIs_ when sticking with one instance type and **not** needing changing it for the **entire**
+ Prefer using _Standard_ RIs when sticking with one instance type and **not** needing changing it for the **entire**
duration of a reservation.
- Otherwise, prefer _Convertible RIs_ for flexibility.
+ Otherwise, prefer _Convertible_ (A.K.A. _Size-flexible_) RIs for flexibility.
RDS does **not** support Savings Plans at the time of writing.
@@ -1146,6 +1157,7 @@ or write workloads and exceeds the instance type quotas.
- [Kyle Kingsbury's Amazon RDS for PostgreSQL 17.4 analysis]
- [AWS RDS Max Connections Limit As Per Instance Type]
- [Amazon RDS and Aurora credentials format]
+- [Amazon RDS: Snapshot, restore, and recovery demystified]
### Sources
@@ -1168,6 +1180,7 @@ or write workloads and exceeds the instance type quotas.
- [Disabling AWS RDS backups when creating/updating instances?]
- [Viewing instance status]
- [Recommended alarms for RDS]
+- [Working With Amazon RDS Snapshots: The Basics and a Quick Tutorial]